Miscellanies. 181 
ally becomes darker and darker, and is ultimately destroyed, owing to 
the action of the light on it. The method I now follow is to put the 
paper into a diluted solution of water of ammonia (one of the spirit of 
hartshorn to about six of water,) and leave it there till the yellow 
parts become white, showing that the phosphate is dissolved, after 
which it is washed with water to carry off the whole of the ammoni- 
acal solution. It should then, when nearly dry, be subjected to pres- 
sure till dried, by which it is prevented from wrinkling, and the im- 
pression retains its original sharpness, which, unless this is done, it is 
aptto lose, by the fibre of the paper being raised by the repeated 
moistening. 
Though the phosphate specimens may be preserved in this way, 
yet they do not retain exactly their original appearance. Those parts 
whitened by the ammonia, owing to part of the silver being united 
With the paper, gradually acquire a faint reddish tinge,—but, though 
altering the appearance, it does not affect the brilliancy; indeed, in 
Some cases it rather improves it, by giving a pleasing tint, which con- 
trasts well with the darker parts, and gives the appearance of color- 
ing. Ihave also found that carbonate of ammonia answers equally 
Well, and, being much cheaper, it will of course be preferred. I gen- 
erally employ a solution, prepared by dissolving one part of salt in 
about four of water, in which the paper is kept for a minute or so, and 
then afterwards washed, and subjected to pressure, as already noticed. 
Impressions thus preserved acquire the same reddish tinge as those 
acted on by ammonia. 
Thave before stated that the paper may be prepared by washing it - 
ver with a solution, procured by adding nitrate of silver to carbonate 
ofammonia. The impressions taken with that paper are easily pre- 
Served by merely washing them with water, to carry off the part not 
acted on by the light, which is another advantage, in addition to those 
Slated, for using the carbonate solution. Like the phosphate speci- 
Mens, they also acquire a reddish tint. 
: Other preservative methods have been recommended, as, by cover- 
ing the impressions with a yellow color, to prevent, as much as possl- 
ble, the transmission of the chemical ray of the light; but those above 
Slated, particularly when the phosphate or carbonate is used, are so 
Simple and efficacious that it is unnecessary to allude to them. 
Before finishing this part of the subject, I may here allude to a val- 
Yable practical application of photography, in diminishing the labors 
of the lithographer. In communicating the impression of any object 
0 the Stone, as of a dried plant, or in copying an engraving, it is ne- 
Cessary to trace them on paper, and after again tracing them with the 
‘ansfer ink, transfer them to the stone. Now, by receiving the im- 
; Pression on paper by the photographic process, all the labor of the 
~ 
